Please see the attached HRTEM and corresponding FFT images of my CNW / VGN sample. I am getting an interlayer spacing of 0.22 nm from ImageJ while strongest spots in FFT gives me 0.33 nm/Cycles.
I know that I should get 0.33 -0.34 nm interlayer spacing for graphene. I do not understand this anomaly.
I have been told that this is not Moire Fringe as dimension of my interlayer spacing is less than actual interplanar spacing of graphene i.e. 0.33 nm.
Hi Rajib,
I just used Gatan and I got the d-spacing of ~0.34 nm. I tried the entire image and I got the same values for the interlayer spacing. See attached as an example You might have not calibrated the image properly.
Hope this helps.
Cheers,
Ahmad
I think the discrepancy is associated to the fact that on the TEM image the interlayer is NOT given by the width of the whitish stripes. Indeed you must take into account the finite width of the dark contrast coming from the carbon layer itself that generate some shrinking of visible interlayer due to widening of the TEM Bragg contrast of carbon layer. Therefore Ahmad Zafari is correct in his analysis which of course agree with the FFT analysis of the image.
Rajib,
I think a brief review through the fundamentals behind the formation of HRTEM images would be helpful.
In general, incident electron wave passes through a very thin sample, and thus, interacts with it so that one direct transmitted wave and a series of diffracted waves are produced. The interference pattern between the direct transmitted wave and the diffracted ones results in contrast due to destructive interactions between some of them (some waves cancel each other out).
Hence, when you get a HRTEM pattern you see some dark and bright columns. The dark areas indicate where the atomic columns are and the bright areas indicate where the atomic columns are not.
Hope you find this useful.
Cheers,
Ahmad
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